In general, rest is as important as can be in functioning innumerable roles for human body, such as energy charge, vitality strengthening, growth, recovery, and immunity strengthening.
Most general rest in one's life is a sleep. There is no better rest than a good sleep. Accordingly, good sleep is important, and although the quality of sleep is affected by indoor temperature and humidity, a pillow leading to a good sleep is physically important.
When one misuses a pillow or sleeps in an abnormal posture, various diseases such as cervical vertebra facet joints disease of the neck, pain in the neck muscle, and ligament damage may be caused. In severe cases, a herniated cervical disc may even be caused. Most ideal sleeping posture is to allow the cervical vertebra to be straight (normal posture), so that muscles are allowed to have no tension.
It is desired to go to bed in a state in which the cervical vertebra is not overstressed such that when sleeping on the back, the neck is allowed to maintain a natural “C” letter curvature, and when sleeping on the side, the cervical vertebra and the thoracic vertebra are aligned in a straight line. Sleeping on one's stomach presses the nerves adjacent to the cervical vertebra and may thus cause numb arms or shoulder discomfort.
Function of a pillow is also important in that the pillow should support the neck while maintaining a normal alignment of the spine, and have a structure suitable for all the heads with various shapes.
When sleeping on the side, the pillow should have height greater than that when sleeping on the back, considering the height of the shoulder.
As a related art to functional pillows, Korean Patent Application Laid-open Publication No. 10-2012-0005893 discloses a functional pillow which is characterized by including: a back head placement part recessed in a shape corresponding to an outer shape of a back head; a cervical vertebra support part extending to a front side of the back head placement part, and formed in a curved surface corresponding to a curve of the cervical vertebra when the back head is placed on the back head placement part; and a flexible space formed such that one rear end of the back head placement part is recessed so as to adjust the size of the back head placement part according to the size of the placed back head of a user.
Also, Korean Patent No. 10-0718661 discloses a head rest for physical therapy characterized by including: a body formed in a cushion member having a predetermined shape and thickness; an upper cervical vertebra acupressure part formed in a curved shape at a predetermined height at one side of the body so as to support the upper cervical vertebra and including a head base acupressure cushion bar attached thereon in a curved shape so as to perform a deep acupressure to the head base portion; a back head acupressure part formed in a curved shape at a lower height than the upper cervical vertebra acupressure part at a position spaced a predetermined distance from the upper cervical vertebra acupressure part, and having a protrusion thereon; and a neck support part formed in a curved shape to incline from the upper cervical vertebra acupressure part.
However, these related arts have no function which maintains the balance of the cervical vertebra by comfortably supporting the neck and head when sleeping on the back and preventing the shoulder pressure or neck deflection when sleeping on the side. Thus, there is a limitation in that the diseases of the neck and shoulder caused by the pressure of the shoulder joint or the torsion of the cervical vertebra, which are frequently experienced by the people sleeping on the side, may not be prevented.